ios - 从 iOS 图像制作视频

我找到了这个教程 http://codethink.no-ip.org/wordpress/archives/673#comment-118063从这个 SO 问题 Screen capture video in iOS programmatically关于如何做这样的事情，它对于 iOS 来说有点过时了，所以我更新了它，并且非常接近它的工作，但是现在将 UIImages 放在一起还不能很好地工作。

这是我在 viewDidLoad 中调用方法的方式

[captureView performSelectorselector(startRecording) withObject:nil afterDelay:1.0];
                            [captureView performSelectorselector(stopRecording) withObject:nil afterDelay:5.0];

和 captureView 是一个连接到我的 View 的 IBOutlet。

然后我有类 ScreenCapture.h & .m

这里是.h

@protocol ScreenCaptureViewDelegate <NSObject>
- (void) recordingFinishedNSString*)outputPathOrNil;
@end

@interface ScreenCaptureView : UIView {
    //video writing
    AVAssetWriter *videoWriter;
    AVAssetWriterInput *videoWriterInput;
    AVAssetWriterInputPixelBufferAdaptor *avAdaptor;

    //recording state
    BOOL _recording;
    NSDate* startedAt;
    void* bitmapData;
}

//for recording video
- (bool) startRecording;
- (void) stopRecording;

//for accessing the current screen and adjusting the capture rate, etc.
@property(retain) UIImage* currentScreen;
@property(assign) float frameRate;
@property(nonatomic, assign) id<ScreenCaptureViewDelegate> delegate;

@end

这是我的 .m

@interface ScreenCaptureView(Private)
- (void) writeVideoFrameAtTimeCMTime)time;
@end

@implementation ScreenCaptureView

@synthesize currentScreen, frameRate, delegate;

- (void) initialize {
    // Initialization code
    self.clearsContextBeforeDrawing = YES;
    self.currentScreen = nil;
    self.frameRate = 10.0f;     //10 frames per seconds
    _recording = false;
    videoWriter = nil;
    videoWriterInput = nil;
    avAdaptor = nil;
    startedAt = nil;
    bitmapData = NULL;
}

- (id) initWithCoderNSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self initialize];
    }
    return self;
}

- (id) init {
    self = [super init];
    if (self) {
        [self initialize];
    }
    return self;
}

- (id)initWithFrameCGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self initialize];
    }
    return self;
}

- (CGContextRef) createBitmapContextOfSizeCGSize) size {
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    bitmapBytesPerRow   = (size.width * 4);
    bitmapByteCount     = (bitmapBytesPerRow * size.height);
    colorSpace = CGColorSpaceCreateDeviceRGB();
    if (bitmapData != NULL) {
        free(bitmapData);
    }
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL) {
        fprintf (stderr, "Memory not allocated!");
        return NULL;
    }

    context = CGBitmapContextCreate (bitmapData,
                                     size.width,
                                     size.height,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     (CGBitmapInfo) kCGImageAlphaNoneSkipFirst);

    CGContextSetAllowsAntialiasing(context,NO);
    if (context== NULL) {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
        return NULL;
    }
    CGColorSpaceRelease( colorSpace );

    return context;
}

static int frameCount = 0;            //debugging
- (void) drawRectCGRect)rect {
    NSDate* start = [NSDate date];
    CGContextRef context = [self createBitmapContextOfSize:self.frame.size];

    //not sure why this is necessary...image renders upside-down and mirrored
    CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, self.frame.size.height);
    CGContextConcatCTM(context, flipVertical);

    [self.layer renderInContext:context];

    CGImageRef cgImage = CGBitmapContextCreateImage(context);
    UIImage* background = [UIImage imageWithCGImage: cgImage];
    CGImageRelease(cgImage);

    self.currentScreen = background;

    //debugging
    if (frameCount < 40) {
          NSString* filename = [NSString stringWithFormat"Documents/frame_%d.png", frameCount];
          NSString* pngPath = [NSHomeDirectory() stringByAppendingPathComponent:filename];
          [UIImagePNGRepresentation(self.currentScreen) writeToFile: pngPath atomically: YES];
          frameCount++;
    }

    //NOTE:  to record a scrollview while it is scrolling you need to implement your UIScrollViewDelegate such that it calls
    //       'setNeedsDisplay' on the ScreenCaptureView.
    if (_recording) {
        float millisElapsed = [[NSDate date] timeIntervalSinceDate:startedAt] * 1000.0;
        [self writeVideoFrameAtTime:CMTimeMake((int)millisElapsed, 1000)];
    }

    float processingSeconds = [[NSDate date] timeIntervalSinceDate:start];
    float delayRemaining = (1.0 / self.frameRate) - processingSeconds;

    CGContextRelease(context);

    //redraw at the specified framerate
    [self performSelectorselector(setNeedsDisplay) withObject:nil afterDelay:delayRemaining > 0.0 ? delayRemaining : 0.01];
}

- (void) cleanupWriter {
    avAdaptor = nil;

    videoWriterInput = nil;

    videoWriter = nil;

    startedAt = nil;

    if (bitmapData != NULL) {
        free(bitmapData);
        bitmapData = NULL;
    }
}

- (void)dealloc {
    [self cleanupWriter];
}

- (NSURL*) tempFileURL {
    NSString* outputPath = [[NSString alloc] initWithFormat"%@/%@", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0], @"output.mp4"];
    NSURL* outputURL = [[NSURL alloc] initFileURLWithPathutputPath];
    NSFileManager* fileManager = [NSFileManager defaultManager];
    if ([fileManager fileExistsAtPathutputPath]) {
        NSError* error;
        if ([fileManager removeItemAtPathutputPath error:&error] == NO) {
            NSLog(@"Could not delete old recording file at path:  %@", outputPath);
        }
    }

    return outputURL;
}

-(BOOL) setUpWriter {
    NSError* error = nil;
    videoWriter = [[AVAssetWriter alloc] initWithURL:[self tempFileURL] fileType:AVFileTypeQuickTimeMovie error:&error];
    NSParameterAssert(videoWriter);

    //Configure video
    NSDictionary* videoCompressionProps = [NSDictionary dictionaryWithObjectsAndKeys:
                                           [NSNumber numberWithDouble:1024.0*1024.0], AVVideoAverageBitRateKey,
                                           nil ];

    NSDictionary* videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:self.frame.size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt:self.frame.size.height], AVVideoHeightKey,
                                   videoCompressionProps, AVVideoCompressionPropertiesKey,
                                   nil];

    videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];

    NSParameterAssert(videoWriterInput);
    videoWriterInput.expectsMediaDataInRealTime = YES;
    NSDictionary* bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
                                      [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];

    avAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput sourcePixelBufferAttributes:bufferAttributes];

    //add input
    [videoWriter addInput:videoWriterInput];
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:CMTimeMake(0, 1000)];

    return YES;
}

- (void) completeRecordingSession {

    [videoWriterInput markAsFinished];

    // Wait for the video
    int status = videoWriter.status;
    while (status == AVAssetWriterStatusUnknown) {
        NSLog(@"Waiting...");
        [NSThread sleepForTimeInterval:0.5f];
        status = videoWriter.status;
    }

    @synchronized(self) {




       [videoWriter finishWritingWithCompletionHandler:^{

           [self cleanupWriter];
           BOOL success = YES;
           id delegateObj = self.delegate;
           NSString *outputPath = [[NSString alloc] initWithFormat"%@/%@", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0], @"output.mp4"];
           NSURL *outputURL = [[NSURL alloc] initFileURLWithPathutputPath];

           NSLog(@"Completed recording, file is stored at:  %@", outputURL);
           if ([delegateObj respondsToSelectorselector(recordingFinished]) {
               [delegateObj performSelectorOnMainThreadselector(recordingFinished withObjectsuccess ? outputURL : nil) waitUntilDone:YES];
           }


       }];


    }

}

- (bool) startRecording {
    bool result = NO;
    @synchronized(self) {
        if (! _recording) {
            result = [self setUpWriter];
            startedAt = [NSDate date];
            _recording = true;
        }
    }

    return result;
}

- (void) stopRecording {
    @synchronized(self) {
        if (_recording) {
            _recording = false;
            [self completeRecordingSession];
        }
    }
}

-(void) writeVideoFrameAtTimeCMTime)time {
    if (![videoWriterInput isReadyForMoreMediaData]) {
        NSLog(@"Not ready for video data");
    }
    else {
        @synchronized (self) {
            UIImage *newFrame = self.currentScreen;
            CVPixelBufferRef pixelBuffer = NULL;
            CGImageRef cgImage = CGImageCreateCopy([newFrame CGImage]);
            CFDataRef image = CGDataProviderCopyData(CGImageGetDataProvider(cgImage));

            int status = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, avAdaptor.pixelBufferPool, &pixelBuffer);
            if(status != 0){
                //could not get a buffer from the pool
                NSLog(@"Error creating pixel buffer:  status=%d", status);
            }
            // set image data into pixel buffer
            CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
            uint8_t *destPixels = CVPixelBufferGetBaseAddress(pixelBuffer);
            CFDataGetBytes(image, CFRangeMake(0, CFDataGetLength(image)), destPixels);  //XXX:  will work if the pixel buffer is contiguous and has the same bytesPerRow as the input data

            if(status == 0){
                BOOL success = [avAdaptor appendPixelBuffer:pixelBuffer withPresentationTime:time];
                if (!success)
                    NSLog(@"Warning:  Unable to write buffer to video");
            }

            //clean up
            CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
            CVPixelBufferRelease( pixelBuffer );
            CFRelease(image);
            CGImageRelease(cgImage);
        }

    }

}

正如您在 drawRect 方法中看到的那样，我保存了所有图像，它们看起来很棒，但是当我尝试制作视频时，它只创建了一个看起来像this，当图像看起来像这样时。

这是输出，它是一个视频，但仅此而已。当图片看起来正常时(不倾斜，很奇怪)

我的问题是制作视频时出了什么问题？

感谢您的帮助和您的时间，我知道这是一个很长的问题。

---

Best Answer-推荐答案

当我想从 CGImageRef(来自 UIImage)创建 CVPixelBufferRef(来自 UIImage)时，由于某些分辨率导致完全相同的视频效果，我发现了这篇文章。

就我而言，非常简短的回答是，我已将每行的字节数硬连接为宽度的 4 倍。以前一直在工作!现在我查询 CVPixelBuffer 本身来获取这个值和 poof，问题解决了!

产生问题的代码是这样的:

CGContextRef context = CGBitmapContextCreate(pxdata, w, h, 8, 4*w, rgbColorSpace, bitMapInfo);

解决问题的代码如下:

    CGContextRef context = CGBitmapContextCreate(
                                             pxdata, w, h,
                                             8, CVPixelBufferGetBytesPerRow(pxbuffer),
                                             rgbColorSpace,bitMapInfo);

在这两种情况下，都设置了 bitMapInfo:

GBitmapInfo bitMapInfo =kCGImageAlphaPremultipliedFirst; // According to Apple's doc, this is safe:  June 26, 2014

关于ios - 从 iOS 图像制作视频，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29552019/